Radio broadcasting system



RADIO BROADCASTING SYSTEI Original Filed 00%. 6, 1923 4 Sheds-Sheet 1L/G/II' J.-

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E. E. CLEMENT 111mm BROADCASTING SYSTEM Original Filed 001:. 6, 1923 a,Z 2 508665,? rat/wave u: EXCl/lA/Gi 200 aecnclc 4/01/7- saw-x44. 07-47704 Sheets-Sheet 2 May 12, 1931. E. E. CLEMENT 1,305,446

mum; BROADCASTING sYsi'nu v Original Filed Oct. 6, 1923 4 Sheets-Sheet 3I U J? L j'lllllllll 3 J IN T L ewe m arc/M70121: (ASTIMW 657' EmmimaMay 12, 1931. E. E. CLEMENT 1,305,445

RADIO BROADCASTING SYSTBI Original Filed Oct. 6, 1923 4 Sheets-Sheet 4Patented May 12, 1931 UNITED; STATES PATENT OFFICE EDWARD E. CLEMENT, OFWASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO EDWARD F. COLLAJJAY, OFWASHINGTON, DISTRICT OF COLUMBIA RADIO BROADCASTING SYSTEM 4 Originalapplication filed October 6, 1923, Serial No. 667,024. Patent No.1,576,309, dated March 9, 1926. Divided and this applicat on filed March8, 1926. Serial No. 93,325.

My invention relates to broadcasting systems. The present application isa division of my prior application, Serial No. 667,024, filed October 6,1923, and patented under date 5 of March 9, 1926, as No. 1,576,309. Fora completely organized system of this kind there are a number ofessentials to be considered which have not yet been rendered availablein pure radio transmission to my knowledge. Among these are, secrecy orrestriction of the service to those alone who pay for it; uniformity andcontinuity of service equal at least to those possible in standard wiredsystem; efiiciency in transmission and fidelity in reproduction;testing, control, metering and supervision of the service from a centralpoint. It will be observed that these requisites of good service callfor means of both distributive and selective character, that is to say,means for distributin the broadcast program or communications to allconsumers in common, and means for individualizing each consumer for anypurpose when necessary. It is the object of my invention to supply thesemeans by superposing an organized broadcasting system upon a combinationof existing wired systems, and without interfering with the ordinaryfunctions of said wired systems, to

. utilize their characteristic forms and arrangement for the appropriateguidance, dis

tribution and control of modulated high frequency or carrier currentwaves as well as direct and alternating current supply, and

the like. Such wired systems are already divided by the nature of theirrespective services into two general classes, distributive systems,including electric light, power and telegraph circuits and somemany-party telephone circuits; and selective systems, includingtelephone exchange systems and all others that have individual wiresleading to the subscribers or consumers.

I attain my object by combining in use these two classes of systems,connecting transmitting and receiving stations to both, i. e.,

to the electric light or equivalent network on one side and to thetelephone line wires on I the other. By this means all the receivingstations or subscribers stations are accessible in common forbroadcasting over the common or distributive medium, and each station isalso accessible individually over the telephone circuit allotted to it,or to which it is allotted. In building up a complete system so as toorganize on an interstate or national scale, this arrangementcontemplates regional distribution, i. e. distribution in territorialdistricts local in character, such as a city or a county, and relayingfrom the national or international sending stations through the regionalor district centers to the local subscribers. The general broadcastingmay be by any known or suitable means either wire or radio orcombinations of wire and radio transmission, which I shall claim herein.

My invention is illustrated as to one form in the accompanying drawings,in which:

Fig. 1 is a schematic diagram indicating the layout of a general systemhaving high power primary broadcasting stations and relayed local orregional distribution;

F i9. 1a is a similar diagram showing wire distribution from a primarystation to local or regional distributing stations.

Figs. 2 and 2a taken together show some detail of the circuits andconnections in the local or regional distribution area, also a metalliccircuit metering scheme.

Referring to Fig. 1, 1, 2 and 3 represent telephone subscribersstations, connected by wires 4, 5 and 6 to the central telephoneexchange C, and all assumed to be supplied with electric light currentover a common wire network indicated at 200, from a central station 7.superposed upon these two wire systems is a broadcast distributionsystem having a central station R fully equipped with switchboards and aline radio or Squier transmitter for broadcasting over the wire network200, with which it is connected as indicated at 208. This station R isalso equipped with receiving and relaying apparatus for diiferent wavelengths, and has access to all lines in the telephone system through theexchange C, as indicated by trunk wires 15. Associated with thetelephone subscribers stations 1, 2 and 3, are broadcast receivers 1a,2a and 3a, each physically connected on one side by wires 10, 20, or 30to the electric light circuit 200, and on the other side by wires 11),2?) or 3?; to an individual telephone line 4, 5 or 6.

In operation, messages or programs broadcasted by means of waveradiation from primary stations as 12, 13 and 14 are received at theregional central station R and relayed through the Squier transmitter bymeans of guided waves or modulated carrier current over the network 200to all the local stations at 1a, 2a and 3a in common, the service beingsupervised, controlled and metered over the individual telephone linesas 4, 5 and 6. Instruments 1a, 2a and 3a are standardized and adjustedto one wave length, so that little or no local tuning is required, alltuning being done at the central station It, the operator there beingable to listen in on the local subscribers receiving instruments overthe telephone wires, and to determine thereby the correct adjustment oftransmitted wave length.

In addition to relaying messages received by radio waves from primarystations, the central station R is equipped with local modulating andSquier transmitting apparatus, for originating programs and distributingthe same over the network 200; and in this connection there are providedtrunk or long distance telephone wire connections for bringing in news,communications or programs from distant points by wire and relaying themout over the local area through the Squier transmitter. I lay no claimto the use of long distance telephone wires per se, but consider the useof the same in combination with the network 200 and the local individualtelephone wires as 4, 5 and 6, to be within the scope of my invention,as creating an alternatiie all wire system which can be depended uponfor maintaining continuity of important service when static or otherconditions make the receipt of radiated waves from primary stationsuncertain, and I shall claim the same accordingly.

Such a combined system, or all wire system, is shown schematically inFig. 1a wherein R indicates a central station similar in all respects tothe station E of Fig. 1. except that in addition to being equipped withradio receiving and relaying apparatus it is also equipped withapparatus arranged to receive broadcast matter transmitted from aprimary station 12 over a wire line or trunk and to relay the samethrough a line radio or Squier transmitter over the wire network 200with which it is connected as indicated at 208.

Other central stations R, R and R are furnished with broadcast matterfrom the primary district station 12 over wired line or trunk circuits.each of which other local distributing stations, R, R and R serve aitretwpzrk 200 similar to that served by the staion In this modificationof the invention, the operation is the same as that of Fig. 1 exceptthat programs received at the several regional central stations from theprimary station 12 are received over wire lines. Any of the regionalstations may also receive by radio from the primary station 12 or otherprimary stations thus giving flexibiliay to the system and greaterassurance of uninterrupted service.

Referring to Figs. 2 and 2a, I have therein shown circuits of thecentral ofiice and substation equipments and connections, Fig. 2representing the telephone side of the system, and Fig. 2a thebroadcasting side of the system. Before proceeding to detail descriptionit may be noted that in accordance with standard telephone practice,provision is made for keeping the telephone lines and central officecircuits clear of all grounds or other disturbing connections duringconversation. When the broadcast receiver goes into service, by closingthe filament switch its operation in receiving is identical with that ofany similar receiver. Each set is provided with a cut off relayenergized when the telephone set goes into commission, either by callingor being called, and at the central office whenever the broadcastoperator takes control of the line, he disables it in the usual mannerby pulling up the cut 011' relay at the telephone switchboard, thishowever being subject to the condition that a special tone test may beput on, so that all operators may now that the line is held on thebroadcast board, and subject to interruption for telephone connection. Iprefer to use this tone test only with the broadcast operators testin gplug, because his regular connecting plug includes within its functionsthat of connecting a subscriber through the station amplifier to thebroadcasting transmitting set, and a connection of this character shouldnot be interrupted without permission.

Referring particularly to the diagram, Fig. 2, A and A are twosubscribers stations connected by line wires 1617 and 18-19,respectively, to the central station C where they terminate on jacks Jand J. PP are plugs forming the terminals of a cord circuit 2021, 22-23,having a bridged repeating coil 1*, ringing and listening keys is and k,supervisory signals ss' and bridging connection to the main battery B.The same battery is shown supplying current to the line relays L, L, andthrough contacts of the cut oit relays L L to the respective lines forcalling purposes. In this system, when a subscriber takes down hisreceiver, the line relay lights its lamp, which is extinguished when theoperator inserts the answering plug. The circuit of the line relay, forexample, relay L, may be traced from battery B through the left handwinding of L, left hand contact of L sleeve line 19, wires l9c19d,through L (Fig. 2a), subscribers telephone set, line 18, right handcontact of relay L right hand winding of L back to rounded side ofbattery B. Battery supp y for the connected lines is thereafter takenthrough the cord circuit 2022, 21-23, in a manner well understood in theart. When the substation telephones are out of service, with theirreceivers hanging on their hooks, the line circuits are conductivelyopen for direct current, leaving the ringers Q, and Q in circuit foralternating ringing current passing through the condensers g-g'.

' Referring now to Fig. 2a, it will be observed that the broadcastswitchboard which I have designated generally by the letter R, isconnected to the subscribers lines by multiple taps marked 16a, 17a, and17 Z), and 18a, 19a, 19?). These terminate on multiple jacks J Jcorresponding to the multiple jacks on the telephone switchboard. Itshould be noted that throughout this system the tip wires 16 and 18 withtheir branches are the grounded wires of the system, while the sleevewires 17 and 19 and their branches, are connected to battery. This isextended into the broadcast side of the system for the purpose ofsecuring proper balance between the main battery or power plant of thatside and the main battery or power plant of the telephone side of thesystem.

At the subscribers stations taps are also taken off from the telephoneterminals to the broadcast receiver terminals as indicated at 180, 190,and 19d. (The receiver is shown only at one substation for sake ofsimplicity of illustration). The two branches 190 and 19d are taken fromthe sleeve or battery side of the line 19, and are connected to oppositeterminals of the winding of a relay L, which constitutes the substationcut off relay for the broadcast receiver. The winding of this rela isbridged by a condenser 9 through w ich both ringing and voice currentscan pass without substantial impedance. Where the broadcast receiver isattached to a party line substation, this relay L may be omitted, sinceon such party lines there are usually grounds on one side or the other.

Normally that is to say when the telephone circuit is not in use the cutofi relay L is deenergized and as a consequence the wire 190 isconnected through a back contact of the relay L through extension wire24 to the branch 25 connected to the A battery marked A in Fig. 2a. Thewire 18c similarly passes through a back contact of the relay to theextension wire 26 leading to test or listening relay L and ground. 18cvit will be remembered leads to the tip or ground side of the line,therefore it is the side which in the broadcasting can be made use ofwith a permanent ground or grounds without disturbing the balance of thetelephone circuit.

The broadcast receiver at the substation A is shown as comprising aninput connection 28 (from the electric light network 200), a tunedcoupler 29, detector tube 30, audio amplifier tubes 31 and 32, and theusual transformers 33, 34, 35, the last mentioned transmitting theamplified audio waves to the telephone receiver or loud speaker 36. Thefilament battery is A The plate battery is B and suitable tuningcondensers and coils, tickler coil for regenerative effects, etc., areprovided as required. I should remark in passing that thisrepresentation of the radio receiver is intended to be typical only. Thepresent invention does not concern itself specifically with the designof the local broadcast receiver sets, and other circuits and apparatusmay be substituted for those shown in the diagrams without departurefrom the invention.

The relay L has four pairs of contacts, one pair 27 a closing the wires25 and 37 from battery A to the filaments. The second pair 27 b closesthe wires 25 and 38 so as to put battery A on the transmitter T, andthrough the induction coil winding to ground. The third and fourth pairsof contacts 27 0, 27d, close the wires 39 and 40, forming terminals ofthe secondary induction coil winding 1, to the tip and sleeve side ofthe telephone line respectively, through the back contacts of relay L.The transmitter T is shown hanging upon a hook switch H controlling theconnection of wires 41 and 42, constituting a parallel link between thebattery A and the filament bus 43. Thus the filament can be heated andthe broadcast receiver put in service either through the agency of therelay L or by the switch hook H. The former is controlled by thebroadcast operator at central, and the latter by the subscriber at thesubstation. In addition to the hook, the subscriber has a manual switchIt by which he can connect the battery wire 42 through a wire 44 to histransmitter T, coil and ground, so as to energize his talking circuit. Iprovide an ordinary telephone receiver t in series with the secondary Iof the induction coil I, and I interpose a pair of condensers g, 9between the secondary I of the induction coil and the telephone receiver25 on the one hand, and the terminals of relay L on the other, so thatwhile the subscriber by means of switch it can connect his telphone T-t'for receiving calls over the telephone line, he cannot originate callsthereover from the broadcast receiver extension.

Returning now to the central station, and particularly to the broadcastdepartment thereof shown in Fig. 2a, T represents a Squier broadcastingtransmitter, symbolized in a very simple form, but supposed to containthe usual elements and connected on the output side with the electriclight or power network 200. This connection includes suitable devices,known in the art, to exclude high voltage and low frequency currents,surges, hum, etc. Suitable switches are assumed located ata convenientpoint. The jack J connected to the amplifier t and thence to thetransmitter T, symbolizes a group of such jacks or equivalent connectingmeans such as automatic switches, controlled by dials or keys, forconnectin any of the wire lines to said transmitter. Letailed appliancesfor receiving radio messages from primary centers, for the switching,and for the local broadcast transmission, are well known in the art, andneed no specific description in this specification.

The cord circuit between plugs P and P in Fig. 2a is the same as theoperators cord circuit in Fig. 2, but the broadcast operator also hasspecial test cords such as that shown in the upper part of the figureconnected to plug P. Here the keys KK' are of standard construction, asin the other cords, and the test contact of the plug P is connectedthrough suitable resistance to the supervisory lamp 8 to the broadcastbattery B, means such as the commutator p being provided to give specialtone test on the test thimbles of the multiple jacks J, J, J etc. Itwill be observed that the constant connection of the sleeve or batterywire 24 at the radiophone substation to the bus wire 25 of the batteryA, produces charging of that battery by the constant flow of currenttherethrough from the main radio battery B at the central ofiice. Thischarging circuit may be traced from battery B through contact of relayL", wire 19a, 19, 19c, contact of relay L, 24, A, and through naturalground back to battery B. The amount of energy thus delivered to thebattery A depends upon the size of the line wires, and the len 'th oftime available for such charging. As shown, the batter wire 24 is notcut ofi except when the cut 0 relay L pulls n which is only when theline wire is in use or conversation. With No. 19 line wires, and usinonly the sleeve wire for conduction, it wou d be possible to safelytransmit from one-half amere to two or three amperes, according to theine resistance and the voltage of the batter emplo ed. Where thisvoltage is standar manua telephone voltage, say 22, and the single wireresistance to the substation is from 25 to ohms, it would be possible tomaintain the battery A continuously charged, provided the time ofdischarge be not too long extended, and the charging be not interruptedby other contingencies, such as the excessive telephone use of the line.

I wish to point out in connection with this, that the art has progressedto a point where filament current required is so small that it is wellwithin the limits of the amperage permissible over the smallesttelephone wires, even continuously flowing, and therefore direct feed ofthe filaments over the telephone wires is not only possible but, forreasons that will be plain to those skilled in the art, will be the bestpractice. It is also possible with instruments now well known to supplyfilament current from electric lighting circuits, as shown for examplein Letters Patent to Lowell No. 1,455,141, May 15, 1923, and both thesemethods of feed are within the sea e of the present invention, owing tomy com ination of these wires into one system.

For metering the subscribers radio service at the central station, animpulse meter which may be of the standard type as indicateddiagrammatically at 50 (Fig. 2) or any known or other suitable typecapable of recording current impulses or circuit closures is employed.This meter is arranged to have its energizing circuit closed through anormally open contact 51 of a relay 52 actuated conjointly with the linelamp, which in the present case is the usual night alarm relay. Foractuating the meter 50 from the subscribers broadcast receiving stationat substantially constant time intervals, a meter actuator in the formof an intermittent circuit closer of any known or other suitable type isprovided. In the present arrangement this actuator 53 is shown as anintermittent thermal switch of the type used as sign flashers. Theenergizing circuit of the actuator 53 including the winding 54 andcontact 55 is connected with the electric light circuit 200 through anormally open contact 56 on the broadcast receiving station switch hookH, while the circuit closing contact 57 is connected in shunt of thesubscribers telephone-transmitter circuit-switch-hook-contacts, so thatupon closure they will effect a closure of the line circuit in t e samemanner as when the subscribers telephone receiver is raised except thatthe closure is momentary or brief and not continuous.

Thus when the radio receiver is in use the switchhook H being in raisedposition maintains the contacts 56 closed which maintain closure of theenergizing circuit of the actuator 53 which circuit may be traced fromthe lower conductor of the power circuit through conductor 58, winding54, contact 55, conductor 59, contact 56, conductor 60 back to the upperconductor of the power circuit. This causes the actuator 53 to warp backand forth and intermittently open and close its own circuit in a mannerwell understood, which causes the contact 57 to be intermittentlyactuated to momentarily close the line circuit at the subscribers endover the following path: contact 57, conductor 61, switch-hook contacta, line wire 18, line wire 19, switchhook h, conductor 62, back tocontact 57. Each momentary closure of the subscribers line circuitefi'ects an actuation of the line relay L in the usual manner as whencalling, except that the actuation is momentary, which in turn efl'ectsan actuation of the meter manna:

50 throu h relay 52 and its contact 51. The circuit 0 relay 52 may betraced from battery B, through winding of relay 52, line lamp andcontact of line relay L back to the grounded side of battery B. Thecircuit of meter 50 may be traced from the free or upper side of batteryB through contact 51 of relay 52, winding 50a of meter 50 and back byway of ground to the grounded side of battery B. The meter 50 as shownis a standard \Vestern Electric line meter of a type in common use.

It has a high resistance winding 50a and a low resistance winding 50?),which causes it to operate as follows: When circuit is first closedthrough the high winding 50a, the

' meter 50 is energized quickly to pull up its armature and close thecircuit of the low resistance or working winding 50?). A rush of currentflows through this low winding, which then actually turns the ratchetwheel of the meter. This could be replaced by any suitable electricallyactuated counting device which would respond to closure of its circiutat the contact 51 of relay 52. Thus, as long as the broadcast receivingstation is in use, the meter 50 is actuated at substantially constantrecurring periods proportionate in number to the time the receivingstation is in use. It is to be noted that while the meter 50 will beactuated once each time the subscriber closes his line circuit ininitiating a telephone call, and that it will not continue to record thetime of use of the radio receiver during use of the telephonesubstation, there will however be no unfairness in the broadcast servicecharge due to the fact that, in practice, the suspension of meteringduring use of the telephone substation will substantially compensate forthe extra actuation of the meter at the initiation of a call.

As stated above, an intermittent circuit closer of any suitable type maybe used in place of the meter actuator 53, for example, any kind of anelectrically operated motor of fairly constant speed may be used toeffect the momentary closure of the telephone line circuit.

A number of modifications in the arrangement of the electric light andtelephone wires in the system thus specifically described can be madewithout departure from the scope of the invention.

Such modifications need not interfere with the ordinary electric energyfeed (battery) over ordinary telephone circuits as usual, but on thecontrary permit full use to be made of the following combination, whichI believe to be novel: (1) energy feed over ordinary telephone circuitsas usual, (2) transmission of filtered wave bands over the telephonecircuits, (3) return of wave bands over other telephone circuits. Thesupply of current energy to the subscribers stations permits 10- calsupply of carrier current component at the subscribers instruments witha minimum of complication.

Summing up, and particularly to make clear terms that will be employedin the claims appended hereto, the following definitions are given: Thelocal area is that containing a group of subscribers such as 1a, 2a and3a in Figs. 1 and 1a. A central station or a regional central station isthat which serves the local area and the subscribers mentioned, therein,such as R in Figs. 1 and 1a. A primary station is one such as 12supplying programs or signals which are to be received and distributedby the station It among its subscribers in the local or regional area. Adistrict station is one such as 12d in Fig. 1a, which serves a number ofcentral stations such as R, R, R R as indicated in Fig. 1a, the saidcentral stations then distributing the program or signals received fromdistrict station 1211!, each in its own local or regional area and toits own subscribers. A district station such as 12d may receive programsby radio or wire from primary stations, such as Iii-14 and may thendistribute the same among the central stations in its district, which inturn will distribute them each to its own local subscriber in its ownregional or local area. In any case, the primary station is that whichoriginates a program or signals, and in this sense the district station120? may also be a primary station for all matters whichit origlnates.

lVhat I claim is:

1. In a broadcasting system, the combination of a central broadcastingstation serving a local or regional area, subscribers stations in saidarea, a common power wire net work connecting said central station andsaid subscribers stations, a primary transmitting station, means fortransmitting broadcast matter from said primary station to said centralstation and means at said central station arranged to relay saidbroadcast matter over said net work to its local subscribers asmodulated carrier current, together with means at each subscribersstation to receive and demodulate said carrier current, and other meansactuated in the operation of said receiving means for signaling betweenthe subscribers station and the central station.

2. In a broadcast distributing system, a district primary station, aregional central station, subscribers stations grouped in the local areaaround said central station, a common power network in said local areaconnected with said central station and said subscribers stations, meansfor transmitting broadcast matter from the district station over anindividual wire circuit to said central station and means at saidcentral station for retransmitting the same therefrom to the subscribersstations over said common wire network, together with means at eachsubscribers station to receive and demodulate said carrier current, andother means actuated in the operation of said receiving means forsignaling between the subscribers station and the central station.

3. In a broadcast distributing system, a primary or district station, aplurality of central or regional distributing stations, a plurality ofsubscribers stations grouped around each central station, a common powerwire network connecting each central station and its local group ofsubscribers stations, individual wire line circuits connecting theprimary or district station with said central stations, means at theprimary station for transmitting a broadcast program Over saidindividual wire line circuits to the different central stations andmeans at each central station for receiving and relaying the saidprogram broadcast to the subscribers in its local area over itsassociated network, together with means at each subscribers station toreceive and demodulate said carrier current, and other means actuated inthe operation of said receiving means for signaling between thesubscribers station and the central station.

4. In a broadcast distributing system, a primary or district station, aplurality of central stations, a plurality of subscribers stationsgrouped in the local area around each central station, means includingtrunk wires for directly transmitting broadcast matter from the districtstation to each of the central stations and means including a power wirenetwork for transmitting broadcast matter from each central station toits group of subscribers stations in common, together with means at eachsubscribers station to receive and demodulate said carrier current, andother means actuated in the operation of said receiving means forsignaling between the subscribers station and the central station.

5. In a broadcast distributing system, a district primary station, aregional central station, subscribers station grouped around saidcentral station, means for transmitting matter to be broadcasted over anindividual line circuit to the central station, a common wire networkconnecting the subscribers stations and the central station, means atthe central station for relaying the matter received thereat over saidcommon network, in-

dividual wire lines connecting each subscribers station with the centralstation, and metering means at the central station controlled over saidindividual wire lines from the different stations.

6. In a system of broadcast distribution, a central broadcast stationand subscribers stations served therefrom, wired power distributingnetwork and a wired telephone exchange system, a broadcast receiving setat each subscribers station, means for transmitting broadcast from thecentral to the subscribers stations over said network, and centralizedmetering means controlled individually from the subscribers stationsover the wires of the telephone exchange system responsive to theoperation of the said subscribers receiving sets.

7 In a system of broadcast distribution, a central station, subscribersstations, a network connecting said stations in common, means at thecentral station for supplying power to said network, means fortransmitting broadcast matter over said network to said subscribersstations, broadcast receiving means and thermionic tubes therefor at thesubscribers stations, means for supplying energy to said tubes derivedfrom said network, a telephone exchange system having individual linewires interconnecting said subscribers stations, and means at thesubscribers stations for connecting and disconnecting the energy supplymeans from the network controlled over said individual lines from acentral point.

8. In a system of broadcast distribution, a central broadcast station ina local area and subscribers stations served therefrom, a local wiredpower distributing network and a local wired telephone exchange system,a broadcast receiving set at each subscribers station, means fortransmitting broadcast matter from said central station to thesubscribers stations over said network, and centralized broadcastmetering means controlled individually from the subscribers stations inthe operation of the said subscribers broadcast receiving sets.

9. In a system of broadcast distribution, subscribers stations in alocal area, local means for supplying power current to said stations, acommon wire network connecting said power supply with said subscribersstations, means at a central point on said network for receivingmodulated waves at radio frequencies, means for reducing saidfrequencies to carrier current frequencies suitable for transmissionover the wire network, receiving instruments at the subscribers stationshaving tunable input circuits connected to said network, and outputcircuits with audio receiving means connected thereto, together withmeans actuated in the use of said receiving instruments to signal saidcentral point.

10. In a broadcasting system, the combination of a central broadcastingstation, subscribers stations grouped in an area around the same, acommon wire network connecting said central station and said subscribersstations, means for furnishing power to said subscribers stations oversaid network, a wired radio transmitting apparatus connected to saidnetwork at a central point, radio receiving instruments connected tosaid network at the subscribers stations, a flasher at a subscribersstation, means actuated in the operation of the radio receivin set atsaid station to communicate current mm the power circuit to saidflasher, and means controlled in the operation of said flasher totransmit signaling current to said central point.

11. In a broadcast distributing system, a district station adapted toreceive modulated waves at radio frequencies, a plurality of central orregional distributing stations, wired connections between said districtstation and said regional stations, a plurality of subscribers stationsgrouped around each regional station, a common wire network connectingeach re ional station and its local group of subscri ers stations, meansin each local or regional area to supply power current over said localnetwork to the subscribers stations, means at the district station forchanging the frequencies received to carrier current frequenciessuitable for transmis sion over the wires, means for transmitting saidmodulated carrier current to the regional stations over the connectingwires, means at each regional station for amplifying and transmittingsaid modulated carrier currents over its local power network, and meansat each subscribers station for receiving and demodulating said carriercurrents.

In testimony whereof I hereunto afiix my signature.

EDWARD E. CLEMENT.

CANADIAN l-TEIITE LOWELL ET AL ESPENSCHIED AFFEL BR. PAT.

REFE1ENCES CITED

